The Components of a Present-day Quality Management System



In electronics, printed circuit boards, or PCBs, are utilized to mechanically support electronic elements which have their connection leads soldered onto copper pads in surface install applications or through rilled holes in the board and copper pads for soldering the component leads in thru-hole applications. A board style may have all thru-hole parts on the top or part side, a mix of thru-hole and surface area install on the top just, a mix of thru-hole and surface mount components on the top side and surface mount components on the bottom or circuit side, or surface area mount components on the leading and bottom sides of the board.

The boards are likewise used to electrically link the needed leads for each element utilizing conductive copper traces. The element pads and connection traces are engraved from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are created as single sided with copper pads and traces on one side of the board only, double agreed copper pads and traces on the leading and bottom sides of the board, or multilayer styles with copper pads and traces on top and bottom of board with a variable number of internal copper layers with traces and connections.

Single or double sided boards consist of a core dielectric material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched away to form the actual copper pads and connection traces on the board surfaces as part of the board manufacturing process. A multilayer board includes a number of layers of dielectric product that has been impregnated with adhesives, and these layers are utilized to separate the layers of copper plating. All of these layers are lined up then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today's innovations.

In a common 4 layer board design, the internal layers are often utilized to offer power and ground connections, such as a +5 V aircraft layer and a Ground plane layer as the two internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Extremely intricate board styles might have a large number of layers to make the different connections for different voltage levels, ground connections, or for connecting the many leads on ball grid selection devices and other big incorporated circuit package formats.

There are typically 2 kinds of material used to build a multilayer board. Pre-preg product is thin layers of fiberglass pre-impregnated with an adhesive, and remains in sheet kind, generally about.002 inches thick. Core product resembles a very thin double sided board in that it has a dielectric product, such as epoxy fiberglass, with a copper layer transferred on each side, usually.030 thickness dielectric product with 1 ounce copper layer on each side. In a multilayer board design, there are two techniques used to build up the wanted variety of layers. The core stack-up method, which is an older technology, utilizes a center layer of pre-preg product with a layer of core material above and another layer of core material below. This combination of one pre-preg layer and two core layers would make a 4 layer board.

The film stack-up approach, a more recent technology, would have core product as the center layer followed by layers of pre-preg and copper product developed above and listed below to form the final number of layers required by the board design, sort of like Dagwood constructing a sandwich. This approach permits the manufacturer flexibility in how the board layer thicknesses are integrated to meet the ended up product thickness requirements by differing the number of sheets of pre-preg in each layer. Once the material layers are completed, the entire stack is subjected to heat and pressure that causes the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.

The procedure of manufacturing printed circuit boards follows the actions listed below for many applications.

The process of determining products, procedures, and requirements to meet the consumer's specifications for the board design based upon the Gerber file information supplied with the order.

The procedure of transferring the Gerber file data for a layer onto an etch withstand movie that is placed on the conductive copper layer.

The traditional process of exposing the copper and other areas unprotected by the etch withstand film to a chemical that gets rid of the unprotected copper, leaving the safeguarded copper pads and traces in location; newer processes utilize plasma/laser etching rather of chemicals to get rid of the copper product, allowing finer line definitions.

The process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a solid board product.

The process of drilling all the holes for plated through applications; a 2nd drilling process is used for holes that are not to be plated through. Info on hole location and size is consisted of in the drill drawing file.

The procedure of using copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are put in an electrically charged bath of copper.

This is needed when holes are to be drilled through a copper location however the hole is not to be plated through. Prevent this procedure ISO 9001 Certification Consultants if possible due to the fact that it includes expense to the ended up board.

The procedure of using a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask secures versus environmental damage, supplies insulation, protects versus solder shorts, and protects traces that run between pads.

The process of coating the pad locations with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will happen at a later date after the elements have actually been positioned.

The procedure of applying the markings for element designations and part lays out to the board. Might be used to simply the top side or to both sides if components are mounted on both top and bottom sides.

The procedure of separating numerous boards from a panel of similar boards; this procedure likewise permits cutting notches or slots into the board if required.

A visual inspection of the boards; also can be the process of inspecting wall quality for plated through holes in multi-layer boards by cross-sectioning or other methods.

The procedure of checking for connection or shorted connections on the boards by means using a voltage in between different points on the board and determining if an existing circulation occurs. Relying on the board complexity, this procedure might require a specifically designed test fixture and test program to incorporate with the electrical test system utilized by the board maker.